Welding is a prevalent method for interconnecting components made of weldable material, such as steel. Exemplary welding methods are resistance spot welding and stud welding, in which two opposite-lying components are interconnected in spots by means of welding. A further welding method is arc stud welding.
In different industries, components that are made partially of non- or poorly weldable material may need to be interconnected nowadays. Nonetheless, welding represents an effective connecting method even for these components made of non- or poorly weldable material. For this purpose, a welding auxiliary joining part made of a weldable material is fastened in the component made of non- or poorly weldable material. A weld connection between a component made of a weldable material and the welding auxiliary joining part is produced below so that the component made of weldable material and the component made of non- or poorly weldable material are interconnected via the welding auxiliary joining part. Examples of components made of non- or poorly weldable material are aluminum sheets, molded parts made of plastic or fiber-reinforced plastic, for example carbon fiber-reinforced plastic, to name just a few examples. The method described above results for example from German patent application DE 100 15 713 A1.
German patent application 10 2005 006 253 A1 describes a connecting method by means of welding between a component made of non- or poorly weldable material and a component made of weldable material. Here, a stud with a shaft and a head made of weldable material is inserted into a prefabricated hole in the component made of non- or poorly weldable material and subsequently welded with the component made of weldable material. In order to reliably fasten the stud with its shaft in the pre-punched area of the component made of non- or poorly weldable material, the shaft of the stud is laterally deformed after welding through compression so that a force-fit connection results between the shaft of the stud and the inner wall of the hole of the component. Due to the plurality of method steps, the connecting method described here is technically complex and time-intensive.
In German patent applications DE 10 2004 025 492 A1 and DE 10 2007 036 416 A1, rivets, studs or nails are set respectively as welding auxiliary joining parts in components made of non- or poorly weldable material. The tip of the welding auxiliary joining part protrudes on the one side of the component made of non- or poorly weldable material and forms a welding spot with a very small contact surface for contacting the opposite-lying component made of weldable material. As soon as the welding auxiliary joining part and the component made of weldable material are interconnected, for example with the aid of resistance welding in the manner of resistance spot welding or resistance stud welding, the tip or edge of the welding auxiliary joining part is melted or fused so that a so-called weld nugget is formed. Due to the small contact surface between the welding auxiliary joining part and the component made of weldable material on the tip or in the cutting area of the welding auxiliary joining part, the contact zone for welding is relatively small. This prolongs the welding process or impairs the weld connection due to the small contact surface compared to opposite-lying components that contact each other in a larger area. Corresponding to the small contact area between the welding auxiliary joining part and the component made of weldable material, the forming weld nugget turns out small. This impairs, among other things, the mechanical loading capacity as well as the lifespan of the established connection. Moreover, in the case of the use of a semi-hollow punch rivet as the welding auxiliary joining part, a waste slug made of non- or poorly weldable material is created. During subsequent welding, it is located in the welding zone and in the area of the weld nugget so that the quality of the forming weld connection is impaired by this contamination.
Furthermore, it is considered advantageous in DE 10 2004 025 492 A1 to mechanically deform the component made of weldable material in the contact area for the later welding with the aid of the setting process of the welding auxiliary joining part made of non- or poorly weldable material in the component. In particular, a tip or an edge of the welding auxiliary joining part penetrates into the component made of weldable material or creates a recess in this component made of weldable material. This recess should then support the formation of a sufficiently large weld nugget during the resistance welding between the welding auxiliary joining part and the component made of weldable material in the area of this depression or respectively recess. However, in order to realize this method, it is necessary to arrange all components to be interconnected above each other before the welding auxiliary joining part is set. Otherwise, additional work is required to create the recess in the component made of weldable material and to align it with the already set welding auxiliary joining parts. This is complex, time-intensive, also requires additional instrumental effort for the exact positioning of the components to be interconnected and is limited in the selection of the possible welding process and the process sequences.
DE 100 60 390 A1 describes a punch riveting method, in which a punch rivet, with the aid of an electrode punch, is forced through a first electrically non-conductive material, such as for example plastic, and is connected with a second electrically conductive material resting on an electrode die. The electrode punch and the electrode die are connected to opposite poles of a voltage source. As soon as the punch rivet has penetrated the first material and is in contact with the second electrically conductive material, a flow of current takes place through the punch rivet. Since the punch rivet heats due to the flow of current, the further joining process of the punch rivet is thereby supported. Since hollow, semi-hollow or full rivets are used in the punch riveting process described here, the punch rivet drives waste material in front during its joining process through the first electrically non-conductive material. This waste material impedes electrical contact between the punch rivet and the second material and thus the flow of current through the punch rivet. It is also disadvantageous that the punch rivet penetrates the electrically non-conductive material in the cold state, which initiates crack formation and other failure mechanisms specifically in brittle plastics and similar materials.
DE 10 2010 020 569 A1 describes a thermal joining of a first electrically non-conductive component with a second electrically conductive component based on an electrical heating. For this purpose, a joining auxiliary means is first molded in the electrically non-conductive component, which is made of an electrically conductive material. In an installation process taking place before the connecting method, the joining auxiliary means is fastened in the first component by means of rolling, stamping, die-forming, embossing, stretch-forming or gluing. The joining auxiliary means provides the electrically conductive contact for the subsequent electrothermal welding with the second component. For this purpose, the first component with the joining auxiliary means and the second component are positioned between an opposite-lying electrode punch and an electrode die. An electrical flow of current through the joining auxiliary means and the electrically conductive second component between the electrode punch and electrode die leads to a welding of the joining auxiliary means and the second component on adjacent boundary surfaces. Even the thermal joining method described here is disadvantageous in that, first in a previous process, an auxiliary joining means must be fastened in the first component made of electrically non-conductive material. Thus, different processing steps of the auxiliary joining means and of the first component are required here before the first component and the second component can be interconnected between the electrode punch and the electrode die.
EP 0 947 279 B1 describes welding tongs for the resistance welding of layers of sheet metal. These welding tongs comprise a welding current source, a welding current control device connected to said welding current source and a local data storage unit, in which process data from the welding tongs can be saved. The welding current control device has data interfaces for the data transfer, via which the saved programs can be transferred from a program memory to the welding current control device. Furthermore, operating data about the welding tongs recorded via such interfaces can be transferred to a memory, where they are stored permanently or temporarily. Known welding tongs and their operating processes are intended to interconnect several layers of weldable material. However, this approach is no longer sufficient from today's design points of view since non- or poorly weldable materials are increasingly present in the connection of several layers of material.
One object that may be achieved by at least some implementations of the present invention is thus to provide alternative devices and connecting methods, with which layers of non- or poorly weldable material can be connected with layers of weldable material.